Background: Epidemiological studies have shown that dairy product consumption is beneficial for cognitive function in elderly individuals. β-lactolin is a lacto-tetrapeptide Gly–Thr–Trp–Tyr rich in fermented dairy products that improves memory retrieval, attention, and executive function in older adults with subjective cognitive decline and prevents the pathology of Alzheimer’s disease in rodents. There has been no study on the effects of β-lactolin on neural activity in humans. Objective: We investigated the effects of β-lactolin on neural activity and cognitive function in healthy adults. Methods: In this randomized, double-blind, placebo-controlled study, 30 participants (45–64 years old) consumed β-lactolin or placebo for 6 weeks. Neural activity during auditory and language tasks was measured through 64-channel electroencephalography. Moreover, verbal fluency tests were performed at baseline and after 6 weeks. Results: The β-lactolin group had a significantly higher P300 amplitude at the Cp2 site (a part of the parietal lobe near the center of brain, p = 0.008), and C4 site (the area between the frontal and parietal lobe, p = 0.021) during the auditory tasks after 6 weeks than the placebo group. Thus, β-lactolin supplementation promoted neural activity in the parietal area, which increases attention during auditory cognitive tasks. Compared with the placebo group, the β-lactolin group also showed significant changes in the scores of verbal fluency test after 6 weeks (p = 0.03). Conclusion: Our findings provide insight into the mechanisms underlying the effects of β-lactolin on attention in healthy adults.

Some studies have asked participants about attentional state on a scale from on-task to off-task, which set the middle option as attention focused on both, including the possibility of the coexistence of thoughts. In addition, studies using multidimensional probes explicitly assumed coexistence within spontaneous thoughts and task-focus dimensions. Although several studies have assumed the coexistence of some thought dimensions, none has explored whether these are different types of thoughts (task-focus, mind-wandering, task-related, external stimuli-related). To examine whether this coexistence of thought types occurred, we used thought probes to determine the degree of immersion in each. The participants responded to probes presented at random during a sustained attention task. The results revealed a mixture of thought types in many self-reports. In addition, the state of attentional allocation behind self-reports was estimated using the hidden Markov model. We observed the following attentional states: task-focused, task-unrelated, task-related, external stimuli-focused, and task-focused—but also focused on other thoughts. These results suggest that individuals can simultaneously allocate attention to thought types and discriminate between reporting. In some cases, probe options should also be considered for this coexistence. We also examined the relationship between self-reports and behavioral indexes, and discussed the necessity of separately measuring the degree of immersion for each thought type.

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